1. Field of the Invention
This invention relates to a process for homogeneously hydrogenating carboxylic acid esters to primary alcohols in solution under mild conditions utilizing anionic Group VIII metal hydride compositions as catalysts.
2. Brief Description of the Background of the Invention Including Prior Art
Carboxylic acid esters, as a class, are not readily susceptible to hydrogenation to produce primary alcohols under mild conditions. Generally, very forcing conditions are required, such as temperatures well above 150.degree. C. together with reaction pressures in the order of 2000-3000 psig. In addition, the hydrogenation process generally requires a heterogeneous catalyst, which are frequently not selective such as Raney nickel, copper-chromite, or zinc-chromium oxide. See Organic Reactions, Vol. 8, pages 1-27 (John Wiley, 1954).
Catalytic hydrogenation of carboxylic acid esters represents an importantindustrial source of primary alcohols, which are useful in a wide variety of known applications such as in producing gums, resins, perfumes, wetting agents and the like. For example, 1-decanol is commercially produced by catalytic hydrogenation of coconut oil fatty acids and their esters under high pressure. Sulfonated derivatives of 1-decanol are useful as surface-active agents. Also, trifluoroethanol, CF.sub.3 CH.sub.2 OH, useful as an intermediate in producing the anesthetic, CF.sub.3 CHClOCHF.sub.2, is produced by the heterogeneous catalytic hydrogenation of trifluoroethyltrifluoroacetate, CF.sub.3 COOCH.sub.2 CF.sub.3, as described in U.S. Pat. No. 4,072,726 (Nychka et al. to Allied Chemical Corporation 1978).
Homogeneous catalytic hydrogenation of acyclic and cyclic carboxylic acid anhydrides to the corresponding esters and lactones by the use of soluble ruthenium catalysts is described in U.S. Pat. No. 3,957,827 (1976) and J.C.S. Chem. Comm. p. 412-413 (1975). However, no specific mention is made of the reduction of esters to the corresponding primary alcohols.
New and improved catalysts for catalytic hydrogenation of carboxylic esters to primary alcohols are constantly being searched for and especially for homogeneous catalysts that can overcome the known attendant disadvantages of the use of heterogeneous catalysts.